Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211957 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 357 PM EDT MON APR 21 2014 .SYNOPSIS...
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HIGH PRESSURE WEAKENS TONIGHT...MOVING FARTHER AWAY. THIS WILL GIVE WAY TO AN APPROACHING COLD FRONT TUESDAY WHICH WILL MOVE THROUGH TUESDAY NIGHT. HIGH PRESSURE SLOWLY BUILDS INTO THE REGION FROM THE WEST WEDNESDAY THROUGH THURSDAY AS A DEEPENING LOW PRESSURE MOVES INTO THE NORTH ATLANTIC. A LOW PRESSURE AND ASSOCIATED FRONTAL SYSTEM IMPACTS THE REGION FRIDAY INTO SATURDAY. HIGH PRESSURE THEN BUILDS IN FROM TH WEST SUNDAY INTO MONDAY.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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A TYPICAL SPRING SCENARIO FOR THE REGION LATE THIS AFTERNOON. WARMEST IN THE LOWER HUDSON VALLEY WITH BOUNDARY LAYER MIXING ALLOWING DEWPOINTS TO BE IN THE TEENS. MEANWHILE SOUTHEAST CONNECTICUT IS THE COOLEST SPOT WITH A LIGHT ONSHORE BREEZE PROMOTING HIGHER DEWPOINTS IN THE LOWER 40S. CLOUDS REMAIN MINIMAL INTO EARLY THIS EVENING AND THIS SHOULD CONTINUE THROUGH MUCH OF TONIGHT WITH THE RESIDUAL SUBSIDENCE OF THE WEAKENING HIGH PRESSURE AREA. THE RIDGE AXIS SLIDES EAST OF THE REGION LATER TONIGHT ALONG WITH THE CUTOFF UPPER LEVEL LOW WELL SOUTH OF THE REGION. AN INCREASING SOUTHWEST FLOW WILL BE DEVELOPING AHEAD OF THE NEXT TROUGH. MAINLY CLEAR SKIES PREVAIL THROUGH MUCH OF THE NIGHT AND WITH A WEAK PRESSURE GRADIENT...THE LIGHT WINDS WILL CONTINUE. WITH THIS...RADIATIONAL COOLING WILL BE MORE OPTIMAL AND ACROSS EASTERN LONG ISLAND AND SOUTHEAST CONNECTICUT...WHERE DEWPOINTS WILL BE RELATIVELY HIGHER...SOME SHALLOW PATCHY GROUND FOG WILL DEVELOP IN THE COOLEST SPOTS. LOWS WERE A BLEND OF 2/3 ECE AND 1/3 MET...FAVORING COLDER SIDE OF MOS GUIDANCE.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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A SHORTWAVE TROUGH DIGS INTO THE OHIO VALLEY TUESDAY. WITH A CONTINUED SOUTH TO SOUTHWEST FLOW IN THE ATMOSPHERIC COLUMN...CLOUDS WILL DEVELOP AND MOVE IN FROM THE WEST THROUGH THE DAY. THIS WILL LIMIT TEMPERATURES AND A DISTRIBUTION SIMILAR TO THE PREVIOUS DAY CAN BE EXPECTED. HIGHS WERE A BLEND OF ECS/MAV/MET GUIDANCE WITH AGAIN COOLER READINGS AT THE COAST WITH MORE ONSHORE FLOW. MODELS ARE IN PRETTY GOOD AGREEMENT WITH DEVELOPMENT OF SHOWERS ALONG THE COLD FRONT. THE PARENT LOW ATTACHED TO IT DEEPENS ABOUT 3-5 MB AS CONVEYED BY DIFFERENT MODELS. THIS WILL COME FROM A STRENGTHENING JET STREAK...INCREASING DIVERGENCE ALOFT. ALSO...INSTABILITY WILL BE INCREASING...MAINLY OVER WESTERN SECTIONS...NORTHEAST NEW JERSEY INTO NYC. MUCAPE UP TO A FEW HUNDRED J/KG IS SHOWN. THEREFORE...EXPECT AN INCREASING CHANCE OF SHOWERS ESPECIALLY LATE IN THE AFTERNOON ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS FOR THE WESTERN AREAS...NORTHEAST NEW JERSEY INTO NYC. FOR TUESDAY NIGHT...THE COLD FRONT MOVES THROUGH LATE EVENING INTO THE OVERNIGHT...SWITCHING FLOW FROM SOUTHWEST TO NORTHWEST. SHOWERS WILL BE WITHIN THE REGION FOR THE FIRST PART OF THE NIGHT AND THEN TAPER OFF FROM NORTHWEST TO SOUTHEAST LATE. LOWS WERE A BLEND OF MET/MAV/NAM12 TO CONVEY TEMPS STAYING UP.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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POTENT UPPER LEVEL SHORTWAVE WILL BE SLOWLY MOVING EAST OF THE CWA AT THE START OF THE LONG TERM PERIOD. SURFACE COLD FRONT WILL BE CLEARING THE AREA WEDNESDAY MORNING WITH DRIER AIR MOVING IN BEHIND IT. THE UPPER LEVEL SHORTWAVE WILL PROVIDE ENERGY FOR AN AREA OF LOW PRESSURE TO DEEPEN ACROSS EASTERN NEW ENGLAND AND THE CANADIAN MARITIMES ON WEDNESDAY. A HIGH PRESSURE SYSTEM WILL BE BUILDING SOUTH INTO THE UPPER MIDWEST AND GREAT LAKES. WITH A TIGHTENING PRESSURE GRADIENT BETWEEN THESE SURFACE SYSTEMS...WEDNESDAY IS SHAPING UP TO BE WINDY WITH GUSTY NORTHWEST WINDS 30 TO 35 MPH. A FEW GUSTS TO 40 MPH CANNOT BE RULED OUT. TIGHT PRESSURE GRADIENT CONTINUES WEDNESDAY NIGHT INTO THURSDAY AS THE OVERALL PATTERN IS SLOW TO CHANGE. THE TROUGH TO OUR EAST BECOMES A CUT-OFF LOW SLOWING DOWN THE PROGRESSION OF THE PATTERN. WINDS ON WEDNESDAY NIGHT WILL WEAKEN A BIT BUT STILL REMAIN GUSTY. GUSTS WILL COME BACK UP ON THURSDAY ALTHOUGH STRONGEST GUSTS MAY BE MORE ACROSS EASTERN ZONES. WINDS FINALLY BEGIN TO SUBSIDE LATE THURSDAY INTO THURSDAY NIGHT AS THE LOW MOVES FAR ENOUGH EAST TO ALLOW A BRIEF SURFACE HIGH AND UPPER LEVEL RIDGE TO BUILD OVERHEAD. ANOTHER SHORTWAVE TROUGH AND ASSOCIATED LOW PRESSURE WILL AFFECT THE REGION LATE FRIDAY INTO SATURDAY. CHANCES OF SHOWERS WILL EXIST FRIDAY INTO SATURDAY...BUT DID NOT GO MUCH HIGHER THAN 30 POP WITH DIFFERENCES APPARENT IN THE MODEL GUIDANCE AT THIS RANGE. THESE DIFFERENCES ONLY GET LARGER INTO SATURDAY AS THE SURFACE LOW BEGINS TO DEEPEN TO OUR NORTH AND EAST. A COLD FRONT SHOULD MOVE THROUGH LATE SATURDAY OR SATURDAY NIGHT. THEN...THE UPPER LEVEL TROUGH ASSOCIATED WITH THIS SYSTEM MAY BECOME ANOTHER CUT-OFF LOW SOMEWHERE OVER THE NORTHEAST SATURDAY NIGHT INTO SUNDAY. CURRENTLY NOT CARRYING ANY POPS SUNDAY...BUT IF THE CUT-OFF IS CLOSE ENOUGH...SOME DAYTIME HEATING INSTABILITY SHOWERS COULD DEVELOP WITH THE COLD POCKET ALOFT ASSOCIATED WITH THE LOW. SURFACE HIGH PRESSURE BUILDS IN FROM THE WEST LATE SUNDAY INTO EARLY NEXT WEEK AS THE CUT-OFF SLOWLY MOVES INTO THE NORTH ATLANTIC. FOR TEMPERATURES...NEAR NORMAL TO SLIGHTLY BELOW NORMAL TEMPERATURES ARE ANTICIPATED WEDNESDAY INTO THURSDAY. FRIDAY AND SATURDAY LOOK TO BE THE WARMEST DAYS IN THE PERIOD WITH HIGHS REACHING THE MIDDLE AND UPPER 60S...COOLEST READINGS NEAR THE COAST. BELOW NORMAL TEMPERATURES THEN RETURN SUNDAY INTO EARLY NEXT WEEK WITH COLDER AIR BEING USHERED IN BEHIND THE LOW TO THE EAST.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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HIGH PRESSURE WILL CONTINUE WEAKENING AS IT MOVES EAST. A COLD FRONT WILL MOVE EAST PASSING ACROSS THE AREA TUESDAY EVENING. VFR WEATHER CONDITIONS ARE FORECAST TO PERSIST UNTIL 18Z TUESDAY. SEA BREEZES ARE FORECAST TO DISSIPATE WITH THE APPROACH OF SUNSET WITH THE STRONGEST WINDS AT KJFK FROM 180 DEGS AT 13 KT BY 20Z. SSW WINDS OF 5 KT OR LESS ARE FORECAST SUNSET-SUNRISE. SSW WINDS WILL INCREASE TO 10-15 KT WITH THE APPROACH OF THE COLD FRONT TUESDAY. THERE IS LOW CONFIDENCE IN THE DEVELOPMENT OF IFR STRATUS AFT 06Z TONIGHT AT KGON. ...NY METRO ENHANCED AVIATION WEATHER SUPPORT... DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE) KEWR FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KJFK FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KLGA FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KTEB FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KHPN FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KISP FCSTER COMMENTS: PATCHY MVFR/IFR CIGS POSSIBLE TO 13Z. .OUTLOOK FOR 18Z TUESDAY THROUGH SATURDAY... .TUE AFT-TUE NIGHT...SHRA BECOMING LIKELY WITH MVFR POSSIBLE. NW-N WINDS G20-25KT AFTER FRONTAL PASSAGE. .WED-THU NIGHT...VFR. NW-N WIND G25-30KT. .FRI-SAT...CHANCE OF MVFR IN SHOWERS FRI AFTN - SAT MORNING.
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&& .MARINE...
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SUB SCA CONDITIONS CONTINUE THROUGH TONIGHT WITH WINDS MAINLY STAYING UNDER 10 KTS WITH WEAKENING HIGH PRESSURE. SOUTHERLY FLOW INCREASING TUESDAY AHEAD OF THE COLD FRONT WITH HIGHER WINDS...10-15 KT GUSTS TO NEAR 20 KT FOR WESTERN OCEAN WEST OF FIRE ISLAND INLET. THE WAVEWATCH GUIDANCE SOMETIMES OVERESTIMATES WAVES WITH SOUTHWEST FLOW SO SCA WILL BE POSSIBLE ON THE OCEAN LATE TUESDAY AFTERNOON BUT SCA WAS NOT ISSUED DUE TO LOW CONFIDENCE AND MORE UNCERTAINTY. GUSTS BECOME MORE FREQUENT LATER TUESDAY NIGHT BEHIND COLD FRONT WITH SCA POSSIBLE AGAIN AS OCEAN SEAS COULD AGAIN REACH 5 FT. TIGHTENING PRESSURE GRADIENT OVER THE WATERS WEDNESDAY INTO THURSDAY. WINDS AND SEAS WILL RISE INTO SCA LEVELS FROM WEDNESDAY THROUGH THURSDAY. THERE IS POTENTIAL FOR GALE FORCE GUSTS WEDNESDAY EVENING INTO THURSDAY MORNING WITH THE BEST CHANCE OVER THE EASTERN OCEAN WATERS. WINDS AND SEAS WILL FALL BELOW SCA LEVELS LATE THURSDAY NIGHT INTO FRIDAY WITH SCA CONDITIONS POSSIBLE ON SATURDAY.
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&& .FIRE WEATHER...
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LOWERING RH VALUES TO NEAR 30 PERCENT AND STRONG GUSTY NORTHWEST WINDS 30 TO 35 MPH WILL BRING FIRE WEATHER CONCERNS ON WEDNESDAY AFTERNOON. THESE CONCERNS CONTINUE THURSDAY AFTERNOON AS EVEN LOWER RH VALUES IN THE 20 TO 25 PERCENT RANGE ARE POSSIBLE THURSDAY WITH CONTINUED STRONG WIND GUSTS.
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&& .HYDROLOGY...
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FOR SHOWERS ASSOCIATED WITH COLD FRONTAL PASSAGE TUESDAY NIGHT...AROUND A QUARTER OF AN INCH OR LESS IS FORECAST. NO HYDROLOGIC PROBLEMS EXPECTED. NO SIGNIFICANT PRECIPITATION IS EXPECTED WEDNESDAY THROUGH EARLY NEXT WEEK. NOTE...MINOR FLOODING CONTINUES ALONG THE CONNECTICUT RIVER. FOR ADDITIONAL INFORMATION...PLEASE REFER TO THE LATEST FLOOD WARNINGS FROM NWS TAUNTON MA.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...JM/DS NEAR TERM...JM SHORT TERM...JM LONG TERM...DS AVIATION...GC MARINE...JM/DS FIRE WEATHER...DS HYDROLOGY...JM/DS

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